This invention relates to audio transducers.
Many different information, entertainment and communication devices having displays have been designed. It is desirable to use such devices to present multimedia, generally in the form of images and sound. Accordingly, such devices require interfaces capable of presenting information both in audio and visual forms.
Personal computers can be used to present real-time multimedia, for example to function as video telephones so that a user is provided with both voice and image of a person with whom he or she talks. A typical personal computer comprises a microprocessor based central unit and a keyboard. The monitor usually comprises a casing containing a CRT (Cathode Ray Tube) typically having a diagonal dimension of at least 35 cm (14 inches). If the personal computer is configured to produce sound, it is convenient to locate a speaker on each side of the CRT either integrated into the monitor casing or provided as discrete units. The personal computer may also comprise a microphone. Integration of the speakers into the monitor casing facilitates initial connecting of peripherals to the computer.
The speakers typically used in these devices are dynamic speakers. Other types of speakers have been suggested. EP 847 670 discloses a CRT monitor which has electrostatic speakers in the form of panels integrated into either side of the monitor casing. The electrostatic speakers integrate a vibrating diaphragm and an actuator to vibrate the diaphragm. Thus, an actuating diaphragm actuates itself to vibrate. This provides a speaker with reduced thickness, but also reduces the length of the maximum movement of the diaphragm resulting in a lower acoustic power per unit area of the diaphragm. Locating such speakers on the sides of the monitor casing allows them to extend from the front of the monitor casing to the back, thus allowing the areas of the sides of the monitor casing to be used while causing only a small increase to its width. However, since the speakers are arranged facing outwardly rather than towards a user, this arrangement directs sound sideways rather than towards the front of the monitor.
In the future it is intended that multimedia should also be presented by mobile stations such as those used in cellular telecommunications systems. Multimedia presentation has been suggested particularly for mobile stations of the so-called third generation. The Nokia(copyright) 9110 communicator is an example of a mobile station presently used to present audio and video signals. This is a multifunction mobile station having two hinged parts. The parts open to reveal a QWERTY keyboard in one part for entry of alphanumeric text and a large LCD-display (Liquid Crystal Display) in the other part for displaying information to a user. This mobile station can wirelessly communicate using fax, e-mail and telephony services. It also allows hands-free (HF) telephone calls to be made using a built-in speaker and a microphone. The speaker is mounted inside the mobile station and sound is conveyed via a specific conduit to the open space surrounding the mobile station. The speaker and the conduit occupy space within the mobile station. Accordingly, in using a speaker arrangement of a particular size a compromise is made between audio quality and space consumption. In addition to the HF-speaker, there is another speaker associated with the earpiece. This further increases the space occupied within the mobile station, and furthermore requires holes to be provided in the mobile station""s casing, which provides entry points for dust and moisture.
As the size of handheld mobile stations such as mobile phones and smart telephones is a limiting factor, it is necessary to select speakers for such devices to be as small as possible. The need to maintain good audio quality and provide a small speaker volume will increase in the future. Additional functionality required to implement the third generation of mobile stations will inherently lead to bigger mobile stations and/or shorter periods of idle time and talk times due to increased power consumption. There is a conflict between very limited size and relatively high power consumption. If the size is limited to a comfortable maximum, it may be too small to hold a sufficiently high-capacity battery, or vice versa, a high-capacity battery that can operate the device for a long period would require too much space. Therefore there is a desire to miniaturise components of mobile stations. However, as speakers are miniaturised, the small size impairs the audio response making reproduced speech and other audio signals difficult to understand and/or less pleasant to listen to.
According to a first aspect of the present invention, there is provided an audio transducer for changing a signal between an acoustic form and an electrical form, the audio transducer comprising an actuating diaphragm, a stator, and a support for supporting the actuating diaphragm adjacent to the stator, characterised in that both the actuating diaphragm and the stator comprise transparent material.
Advantageously, the audio transducer can be placed between a user and an object such as a screen without preventing the user from seeing the object, since the actuating diaphragm and the stator are transparent. This allows the transducer to be placed in front of objects that need to be seen.
According to a second aspect of the present invention, there is provided an audio-visual device comprising
an optical device, and
an audio transducer for changing a signal between an acoustic form and an electrical form, the audio transducer comprising an actuating diaphragm, a stator, and a support for supporting the actuating diaphragm adjacent to the stator, characterised in that
both the actuating diaphragm and the stator comprise transparent material and
the audio transducer is arranged adjacent to the optical device.
It is advantageous to combine a transparent audio transducer and an optical device. Thus, the very same area can be used to output or input image and to output or input sound or voice.
Preferably, the actuating diaphragm is arranged to vibrate in response to an electrical signal interacting with the actuating diaphragm to generate an acoustic response. Alternatively, the actuating diaphragm is arranged to vibrate in response to an acoustic signal interacting with the actuating diaphragm to generate an electrical response.
Preferably, the audio transducer is a speaker, a microphone, or a combination of both. In an embodiment of the invention in which the audio transducer is a transparent element disposed between a user and a display, this may provide a relatively large display surface area to be used as an acoustic element.
The optical device may be a mobile station, a mirror, a window, an electrical display, a solar cell, a touch screen or an illuminator. An electrical display is a display device comprising a screen, an input for receiving an electrical input signal and means for displaying on the screen texts or images corresponding to the electrical input signal.
Since the invention allows the surface area needed for a display to show information to be used for the audio transducer, a compact size of user interface device can be made with an audio transducer not smaller than the screen. This allows manufacture of smaller user interface devices and manufacture of user interface devices of ordinary size, but with an improved audio quality. Alternatively, if the optical device is a solar cell, then the surface of the solar cell can be used also to output sound, and efficiency of surface usage improves. If the audio response originates from the region of the optical device, the audio response appears, to a user, to come from the optical device. A display according to the invention used for video conferencing gives a realistic impression when the sound appears to come from the display. A rear-view mirror may be arranged to tell a user how far an object is behind a vehicle. A window of a shelf in an exhibition may tell about a particular exhibit.
Preferably, the audio-visual device is a mobile station further comprising a radio block for radio communication.
Preferably, the display is arranged to be visible through the actuating diaphragm.
An advantage of the invention is that the diaphragm of the transducer itself carries out the conversion between acoustic and electrical forms of signals. Dedicated movement conversion elements such as coils or magnets are not necessary. Thus, the transducer requires only a small depth in which the diaphragm may be located to vibrate. Additionally, providing the transducer on the outer surface of an optical device (adjacent to, for example, a display or a solar cell) makes it unnecessary to provide a sound-conveying conduit. This frees some space within the casing of the device for other components or allows manufacture of smaller devices without reducing functionality. A transducer provided by the invention has a relatively large surface, which also increases the maximum sound pressure when the transducer is used as a speaker and increases the sensitivity of the transducer when the transducer is used as a microphone. Furthermore, when the transducer is used as a speaker, sound appears to come from the image rather than from one side. Correspondingly, when the transducer is used as a microphone, a user is able to speak directly at the display and the transducer is able to receive the speech efficiently.
Preferably, the display is used as a stator for the actuating diaphragm. This reduces number of parts required.
Preferably, the actuating diaphragm is located between an outer protective diaphragm and the display so as to protect the actuating diaphragm from mechanical damage. In this case, the outer protective diaphragm allows a user to see through it. It may be transparent. Preferably the outer diaphragm is electrically conductive and arranged additionally to function as a stator for the actuating diaphragm. Preferably, the outer diaphragm is made of a material that allows sound waves to travel through itself in order that sound produced by the transducer is audible to a user of the audio-visual device. The outer protective diaphragm may be made of a porous material or provided with openings. Alternatively a grid could be used to protect the actuating diaphragm whilst also allowing the sound waves to be conveyed from the actuating diaphragm to space surrounding the audio-visual device.
Preferably, the actuating diaphragm is used to produce sound for an earpiece of an audio-visual device in addition to providing sound from the display.
According to a third aspect of the present invention, there is provided a method of producing an audio-visual response, wherein a transparent and electrostatic actuating diaphragm is arranged in a nominal position adjacent to an electrical display. The method comprises the steps of:
displaying an image on the electrical display, and
feeding an electrical audio signal to the actuating diaphragm to cause it to vibrate in order to generate a sound.
Advantageously, the method gives a user an impression of sound originating from the electrical display.
According to a fourth aspect of the present invention, there is provided a method of manufacture of a device comprising a display, a speaker, and a transformer to drive the speaker, comprising the steps of:
attaching a transparent actuating speaker diaphragm adjacent to the display, and
coupling the transparent actuating diaphragm to the transformer to drive the transparent actuating diaphragm as a sound producing vibrating element.
The present invention enables production of a compact and lightweight device by integration of a display and speaker so that they both occupy the same area. Therefore, there is no need to leave openings for a speaker in the casing of the device and penetration of dust and moisture into the device can be largely avoided. In addition, the production process becomes simplified, because separate openings need not to be made for arranging audiophonic access between the speaker and the space surrounding the device.
The present invention is applicable to devices such as mobile phones, electrical games, and wireless telephones, as well as to bigger devices such as laptop computers or displays for desktop computers. It is particularly suited to thin displays such as LCDxe2x80x94or electroluminescence displays. In general, the present invention may be used in applications where there is lack of space and a relatively large display is required.